Selling parts and lack of manners.

Ok, so here's the problem I keep having as a seller! I list a part, I get a message right away cause I must be selling at a good price, I message the first guy in line and mark him as the buyer and ask for his zip! Boom, 3 other people say ill take it too before I can even get to the thread to post a sale pending on the item post! I post sale pending in the thread but maybe not everybody reads that, so people who messaged saying ill take it may not know that! Next thing you know, there are 7 people (true) who want the part while I was posting a sale pending in the thread!

Do I have to message everybody personally to alert them of their place in line? From my phone? And then go through the 300 messages I have in my message folder and delete the 6 from this sale, the 3 from the previous 27 sales, all from my phone?

And because everybody is following the rules much better now, no one is posting a "PM Sent" to mark their place in line on the thread, so other than my post, which may or not be read, there appears to be no interest at all in the item!!

Happening just about every listing now, and I'm only listing a couple items at a time!! What should I do the make the masses happy?......